Method of temperature control in chemical reactions



MTATW OF l-w la at e EDGME, '15 WASHINGTON, DISTRICT OF UOLUMBIA; MSIGNOE, lid h l l ED in AS REPRESENTED BY THE SECRETARY 0W WM rtnrnon or rmurnna'runn con'rnonrit cnmurcannniacrmns.

' the brewing.

To all whom it may concern:

Be it known that l, GRAHAM EDGAR, a citizen of the United States, residing at Washington, District of Columbia, have int vented an llmprovement in Methods of Temperature Control in Chemical Reactions, of which the following is a specification.

This invention relates to the promotion of chemical reactions for its objects the conto. venient and economical temperature control during reactions between solids and fluids, especially solids and concentrated a.cids.-

"l-lleretofore, one ofthe serious problems encountered in industrial chemical processes it was that of the disposition of the reaction heat andthe regulated control of the temperatures of the reacting mass, particularly in large scale operations.

in the case of reactions in whichonly as liquid phases are concerned, various types of refrigerating device's are employed with reasonable success, and inthe case of reactions in which only the gaseous phase occurs, heat interchangers are successfully employed, but in the case of reactions between sohds'and li uids, or between solids and gases, and. in a cases where the prodnets of reaction are solid or semi-solid, the disposal of he heat of reaction and the control of temperature are much more difficult; r My investigations have shown that proper tern erature control may beefi'ectively achieved in such reactions by causing at least one of the reacting substances to be suspended in finely divided condition'in air or other as at the time of reaction. Thus a finely 'vided suspension ofa solid substance in an air current may be brou ht 'in contact with a fine mist of liquid and al owed to react or afinely divided suspension of a solid substance in air or other as may .be passed directly into a body of iquid with which it will react; or, a ain, a

finely divid- M ed suspension of la soli substance in air till or other gas may be mixed-with a gas with which it will react. in any case, it is pomible to'control the temperatureof the reaction and dissipate the eat of reaction w by legal 1 ting the concentration of the sus- J p ded substance in the gaseous medium, mince large or small amount of heatwill be up to the gaseous medium, accordmgly as the eoncenh'ation of the reactin or low. In all t Ill? m substance id l application tiled January 3, 1929 Serial No. eraser.

eases the gaseous medium serves to absorb such part of the heat of reaction as may be desired by its own heat absorption capacity, and also in those cases in which liquid phases are involved, through causing some evaporation of the liquid to occur.

Various mechanism of well known types may be employed for carrying out my improved process, the same varying somewhat with the nature of the substance. Thus, for example, liquids may be formed into a fine mist by means of such nozzles as are used in commercial sprayingh devices, or by other means, and on the'ot or hand. finely divided suspensions of solids may be, for example, formed by introducing the finely ground solid into a current of air .byutilizing such devices as is used in the carburetors of the wellknown powdered coal burners.

An, example of. a reaction in which the application of this principle may be found advantageous is that between calcium cyanamide and sulfuric acid. It has been-often pro osed that many of the objectionable qu ities of calcium cyanamide-may be overcome, and useful nitrogeneous fertilizers formed, by the treatment of the calcium cyanamide with sulfuric acid. However, the very large amount ofheat accompanying the reaction has made the control of temperature so dificult that prior to my invention, satisfactory, practical and economical conditions of reaction with the consequent production of a satisfactory dproduct, do not seem to have been achieve In carrying out my preferredprooedure, it may proceed as followsz Finely ground calcium cyanamide is sue-- pended in an air current by any intake means, such, for example,as above indicated, and themixture is then brought in contact with a fine mist or spray of sulfuric acid in the proportions in which itis de sirw that the-substances should react. B this pi'ocedure, usin given quantities of ca 1W cium 'cyanamide an sulfuric acid, the temperature of the reaction maybe regulated at will by regulating the amount of air mined I with the calcium cyanamide'and by regulating the finenms of the acid spray, there by rendering it possible to maintain a temperature that is most suitable to obtain the particular reaction product desired.

For example an efiective yield of urea can be obtained by bringing l1 arse in parts of sulphuric acid (figured on the basisof 100% acid) in the form of a 15 normal so.-

lution, i. e. 734 grs. per liter, with 2000 parts of cyanamid' suspended in an air Gurrent. By employing the foregoing cooling' means, the destructive decomposition of the c anamid or thearea formed therefrom wi prevented, provided the temperature is held below the boilingpoint, and preferablyfrom The excess acid in the product obtained from the above described treatment of cyanamid and sulphuric. cid can profitably be neutralized with finely ground phosphate rock in the proportion of about 1200. parts of 70% native phosphate rock 100 to 200 mesh)v with every 2000 parts of, cyanamid treated. I

tively to control the temperature,

' Not only do the air currents serve effecbut they also serve, because of their tendency to 'entrain moisture, as dehydrating agents, with a consequence of the resulting roduct from the treatment'ofcyanamid w1 be reasonably granular and dry, i. e. non-pastry or not objectionably sticky and will-upon exposure to the air rapidly dry out sufliciently to be packed for shipment without further treat-- ment. I a p The obj ection to the employment of weak acid and reaction as the foregoing, is not only because of the fact that the introduction of'uiinecessary water requires the subsequent removal of the same, and unnecessarily expensive procedure, but also as in the case ofproductio'n of urea from cyanamid, an efl'ective yield of the desired product is .not obtainable when employing dilute acid.

Having thus described my invention, what I clann and desire to secure by Letters Pat .ent of the United States'is 1. The-process for controlling the tem- 'to the gaseous medium and perature of the reaction between calcium cyanamid and sulfuric acid which consists in suspending one of such substances in a current of air and then causing them to contact with each other.

2. The process for controlling the temperature of thereaction between calcium cyanamid and sulfuric acid which consists in suspending calcium cyanamid in a current 0 air and then causing the same to re act with liquid sulfuric acid brought into contact therewith.

3. The process for controlling the temperature of the reaction between calcium cyanamid and mineral acid which consists' suspending the calcium cyanamid in a finely divided condition in a gaseous medium, controlling the ratio of the cyanamid to the gaseous medium, and then bringing it in contactw'ith the mineral acid.

6. The process for-controlling the tem perature of reaction between calcium cyanamid and a mineral acid, which consists in suspendin oneof them in a gaseous medium and then ringing the other substance into contact with the suspended substance.

' GRAHAM EDGAR. 

